Exposure to daily mean and maximum 1-hour PM concentrations and pediatric respiratory mortality in the Mexico City Metropolitan Area.

Background: Few studies have evaluated the association between short-term PM exposure and children's respiratory mortality. This study examines the relationship between daily mean and maximum 1-hour PM exposures and age-specific pediatric respiratory mortality, addressing a gap in understanding the effects of subdaily PM peaks.

Methods: We analyzed ICD-10-coded mortality records (n = 90,566) from the Mexico City Metropolitan Area (2004-2019). PM exposures came from our satellite-based models for daily mean and maximum 1-hour concentrations. Using a time-stratified case-crossover design and conditional logistic regression with distributed lags, we examined associations between PM and nonaccidental mortality, and specific respiratory conditions (e.g., influenza, pneumonia, bronchopulmonary dysplasia) across neonates, infants, children, and adolescents, accounting for sex-based effect modification. Our models included negative control exposures to address potential confounding.

Results: Among all age groups, infants were the most affected by daily mean and maximum 1-hour PM concentrations. Mean PM was associated with higher risk of respiratory, and influenza and pneumonia mortality in infants. In the same age group, an increase of 10 μg/m in the maximum 1-hour PM concentration was associated with nonaccidental (odds ratio [OR][lag] = 1.02 [95% confidence interval {CI}: 1.00, 1.03]), respiratory (OR[lag] = 1.04 [95% CI: 1.02, 1.06]), influenza and pneumonia (OR[lag] = 1.05 [95% CI: 1.02, 1.08]), and bronchopulmonary dysplasia-related (OR[lag] = 1.07 [95% CI: 1.00, 1.15]) mortality. Our results suggest effect modification by sex in the association between mean PM and respiratory mortality, with positive associations observed primarily in male neonates and adolescents.

Conclusions: Our study contributes to the evidence on the association between daily PM exposure and pediatric respiratory mortality, while also revealing new insights into the impact of maximum 1-hour PM on age- and cause-specific respiratory mortality.